Electric discharge tube



May 1?, 1932. J. H. DE BOER ET AL ELECTRIC DISCHARGE TUBE Filed Nov 26, 1929:

- INVENTORS K M VAN GESSEL BY J. D BOER 2 WM, ATTORIIEY Patented JAN HENDRIX DE BOER AND KABEL MARINUS VAN GESSEL, OF EINDHOVEN, NETHER- LANDS, ABSIGNORS TO DIO CORPORATION OF AMERICA, A CORPORATION OF BEWARE ELECTRIC DISCHARGE TUBE Application filed November 26, 1929, Serial No. 409,804, and in the Netherlands December 15, 1928.

This invention has reference to an electric discharge tube, more particularly an incandescent cathode discharge tube.

It is well known to remove the gaseous 5 residues which after exhaustion remain in an electric discharge tube or the impurities of the gaseous filling of a discharge tube, prior to putting the tube into use, by volatilizing within the tube a suitable material,

10 for example, magnesium. This volatilization is usually efiected by heating a supply 'of the so-called getter material introduced into the tube to the temperature of volatilization by means of induction currents generated by a high frequency magnetic alternating field. The material volatilized is thus precipitated on the colder parts of the tube and the gaseous residues or impurities are vinculated or absorbed.

It has been found that in many discharge tubes undue gases are set free even during the operation of the tube. These are, for example, gases which were occluded in the electrodes and which are set free. by these members in consequence of some heating during the operation of the tube. In the majority of cases it is highly desirable that these gases, which exercise an unfavorable influence on the discharge phenomena in a discharge tube, should be Withdrawn from the atmosphere of the tube.

The invention has for its object an electric discharge tube in which means are provided which render harmless any gaseous residues 5 or impurities set free during the operation of the tube, in a simple and easy manner.

' An electric discharge tube according to the invention comprises an incandescent cathode which has connected in parallel to it a conductor made of a substance which is capable of vinculating or absorbing gaseous residues or impurities at high temperatures. Preferably, this conductor is made of a substance of high specific electric resistance so as to permit small consumption of the current passing through this conductor. Very good results may be obtained by constituting the conductor of zirconium. Although other metals such as tantalum, molybdenum,- titanium, chromium, and aluminum may be used, it has been found that the best results are obtained with zirconium.

It is frequently desirable that the conductor should not be connected in parallel to the incandescent cathode until after the exhaustion of the discharge tube, as otherwise the conductor may acquire too high a tem perature during exhaust. In order to obviate this difiiculty one end of the conductor may be connected to a separate leading-in wire which is taken through the wall of the tube. After the exhaustion of the tube this wire may be connected to a leading-in wire of the incandescent cathode.

The invention will be more clearly understood by reference to the accompanying drawing, which shows by Way of example an electric discharge tube embodying the invention.

The discharge tube 1 shown in the figure is exhausted to the highest extent possible, and comprises a stem 2 having a pinch 3 on which the various electrodes of the tube are arranged. These electrodes comprise a cylindrical anode 4, which is supported upon a supporting wire 5, a grid 6, and a filament 7. The grid 6 is secured to a wire 8 supported upon the supporting rods 9 and 10. The incandescent cathode is secured to the sup ports 11 and 12 which have also mounted between them a wire 13 of zirconium, the dimensions of which wire are such that during the operation of the tube the wire is heated to such a high temperature that it vinculates or absorbs gaseous residues which may be set free during the operation of the tube.

It is, of course, obvious that the invention does not only extend to high vacuum discharge tubes such as valves for wireless telegraphy or telephony, X-ray tubes, rectifiers, etc., but alsoto discharge tubes having a gaseous filling, such as gas-filled rectifiers, for example tubes having a filling of rare gas to which metal Vapor, say mercury vapor, may be added.

What we claim is:

1. In an electron discharge device, the combination with an evacuated envelope containing co-operating electrodes one of which is heatable and a pair of current supply leads connected to said heatable electrode, of a coherent body of zirconium of high electrical resistance connected during normal 0 eration of said device to said leads where y sufficient current passes through said heatable electrode and said body to maintain said electrode at operating temperature and said body at a temperature which renders it capable of combining permanently with the common occluded gases in said envelope.

2. In an electron discharge device, the combination with an evacuated envelope, an electrode therein, a co-operating heatable electrode, and a pair of current carrying leads connected to said heatable electrode, of an elongated body of zirconium in said envelope permanently connected to said leads in parallel to said heatable electrode and of such electrical resistance as to be maintained during normal operation at a temperature which renders it capable of combining permanently with the common occluded gases in said envelope.

3. An electron discharge device comprising a sealed envelope containing a heatable electrode and a co-operating electrode, a pair of conductors extending into said envelope, and a coherent body of zirconium connected to said heatable electrode in said envelope electrically connected to and mounted between said conductors and of an electrical resistance such that at normal operating potential on said conductors said body is maintained at a temperature which renders it capable of combining permanently with the common occluded gases in said envelope.

4. An electron discharge device comprising a sealed envelope, a pair of conductors extending into said envelope, a heatablecathode comprising a refractory filament connected to said conductor and a zirconium filament connected to said conductors in parallel to said refractory filament and proportioned to operate at normal voltage between said conductors at a temperature which renders it capable of combining permanently with the common occluded gases in said envelope.

JAN HEN DRIK DE BOER. KAREL MARINUS VAN GESSEL. 

